1. Field of the Invention
The present invention relates to a method and apparatus for forming a non-single-crystal layer on a substrate, and more particularly to a method and apparatus for forming a non-single-crystal layer which are suitable for the manufacture of semiconductor photoelectric conversion devices for use as solar cells.
2. Description of the Prior Art
Heretofore there has teen proposed a method according to which a material gas for forming a non-single-crystal layer is introduced into a reaction chamber and is excited to form the non-single-crystal layer by deposition on one or more substrates disposed in the reaction chamber.
With such a conventional method, the material gas is introduced into the reaction chamber to fill it up and, consequently, the excited material gas not only passes over the substrates but also unnecessarily flows everywhere in the chamber. Accordingly, the utilization rate of the material gas is as low as about 1 to 3% and, further, the non-single-crystal layer is formed at as low a rate as approximately 0.1 to 2 .ANG. per second.
Moreover, since the excited material gas allowed to flow in contact with the inner wall of the reaction chamber, flakes formed by the excited material gas stick to the inner wall of the reaction chamber, and they often fall off onto the substrate. Accordingly, it is very likely that the non-single-crystal layer contains therein the flakes or has a number of pin-holes resulting from the bombardment by the flakes.
According to the prior art method, in the case of exciting the material gas by ionizing it into a plasma through the use of high-frequency electrical energy, the direction of its electric line of force is selected to cross the substrate. On account of this, the non-single-crystal layer may sometimes be damaged due to sputtering by the excited material gas, i.e. the material gas plasma.
Furthermore, in the case of using high-frequency electrical energy which is obtained across a pair of electrodes, the material gas is excited in such a state that the potential of either one of the electrodes is being applied to the substrate. With this method, however, undesirable flakes formed by the excited material gas stick to the substrate surface, resulting in the non-single-crystal layer containing the flakes in quantity.
A conventional non-single-crystal layer forming apparatus for the abovesaid method naturally possesses such defects as mentioned above.